[SPARK-4535][Streaming] Fix the error in comments

change `NetworkInputDStream` to `ReceiverInputDStream`
change `ReceiverInputTracker` to `ReceiverTracker`

Author: q00251598 <qiyadong@huawei.com>

Closes #3400 from watermen/fix-comments and squashes the following commits:

75d795c [q00251598] change 'NetworkInputDStream' to 'ReceiverInputDStream' && change 'ReceiverInputTracker' to 'ReceiverTracker'

examples/src/main/scala/org/apache/spark/examples/streaming/StatefulNetworkWordCount.scala

@@ -64,7 +64,7 @@ object StatefulNetworkWordCount {
     // Initial RDD input to updateStateByKey
     val initialRDD = ssc.sparkContext.parallelize(List(("hello", 1), ("world", 1)))
 
-    // Create a NetworkInputDStream on target ip:port and count the
+    // Create a ReceiverInputDStream on target ip:port and count the
     // words in input stream of \n delimited test (eg. generated by 'nc')
     val lines = ssc.socketTextStream(args(0), args(1).toInt)
     val words = lines.flatMap(_.split(" "))

examples/src/main/scala/org/apache/spark/examples/streaming/clickstream/PageViewStream.scala

@@ -50,7 +50,7 @@ object PageViewStream {
     val ssc = new StreamingContext("local[2]", "PageViewStream", Seconds(1),
       System.getenv("SPARK_HOME"), StreamingContext.jarOfClass(this.getClass).toSeq)
 
-    // Create a NetworkInputDStream on target host:port and convert each line to a PageView
+    // Create a ReceiverInputDStream on target host:port and convert each line to a PageView
     val pageViews = ssc.socketTextStream(host, port)
                        .flatMap(_.split("\n"))
                        .map(PageView.fromString(_))

streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala

@@ -187,7 +187,7 @@ class StreamingContext private[streaming] (
   /**
    * Set each DStreams in this context to remember RDDs it generated in the last given duration.
    * DStreams remember RDDs only for a limited duration of time and releases them for garbage
-   * collection. This method allows the developer to specify how to long to remember the RDDs (
+   * collection. This method allows the developer to specify how long to remember the RDDs (
    * if the developer wishes to query old data outside the DStream computation).
    * @param duration Minimum duration that each DStream should remember its RDDs
    */

streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingContext.scala

@@ -479,7 +479,7 @@ class JavaStreamingContext(val ssc: StreamingContext) extends Closeable {
   /**
    * Sets each DStreams in this context to remember RDDs it generated in the last given duration.
    * DStreams remember RDDs only for a limited duration of duration and releases them for garbage
-   * collection. This method allows the developer to specify how to long to remember the RDDs (
+   * collection. This method allows the developer to specify how long to remember the RDDs (
    * if the developer wishes to query old data outside the DStream computation).
    * @param duration Minimum duration that each DStream should remember its RDDs
    */

streaming/src/main/scala/org/apache/spark/streaming/dstream/ReceiverInputDStream.scala

@@ -29,7 +29,7 @@ import org.apache.spark.streaming.scheduler.ReceivedBlockInfo
 /**
  * Abstract class for defining any [[org.apache.spark.streaming.dstream.InputDStream]]
  * that has to start a receiver on worker nodes to receive external data.
- * Specific implementations of NetworkInputDStream must
+ * Specific implementations of ReceiverInputDStream must
  * define `the getReceiver()` function that gets the receiver object of type
  * [[org.apache.spark.streaming.receiver.Receiver]] that will be sent
  * to the workers to receive data.
@@ -39,17 +39,17 @@ import org.apache.spark.streaming.scheduler.ReceivedBlockInfo
 abstract class ReceiverInputDStream[T: ClassTag](@transient ssc_ : StreamingContext)
   extends InputDStream[T](ssc_) {
 
-  /** This is an unique identifier for the network input stream. */
+  /** This is an unique identifier for the receiver input stream. */
   val id = ssc.getNewReceiverStreamId()
 
   /**
    * Gets the receiver object that will be sent to the worker nodes
    * to receive data. This method needs to defined by any specific implementation
-   * of a NetworkInputDStream.
+   * of a ReceiverInputDStream.
    */
   def getReceiver(): Receiver[T]
 
-  // Nothing to start or stop as both taken care of by the ReceiverInputTracker.
+  // Nothing to start or stop as both taken care of by the ReceiverTracker.
   def start() {}
 
   def stop() {}

streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverTracker.scala

@@ -46,7 +46,7 @@ private[streaming] case class DeregisterReceiver(streamId: Int, msg: String, err
   extends ReceiverTrackerMessage
 
 /**
- * This class manages the execution of the receivers of NetworkInputDStreams. Instance of
+ * This class manages the execution of the receivers of ReceiverInputDStreams. Instance of
  * this class must be created after all input streams have been added and StreamingContext.start()
  * has been called because it needs the final set of input streams at the time of instantiation.
  *